This invention relates to an oil pressure absorbing apparatus in an impact type tool used chiefly for tightening by rotation of a screw member such as a bolt, a nut or the like.
Such types of tools have been hitherto known where an eccentric oil chamber formed in a rotatable cylinder connected to a driving source such as an air motor or the like, is provided with a rotor connected to a spindle, so that every time the rotor reaches a predetermined angular position during its relative rotation in relation to the oil chamber, oil is confined in respective partitioned chambers formed on both sides of the rotor and the rotor is thereby given an impact torque. In this case, due to temperature rise during use of the tool, the oil increases in temperature and expands. Thus, the output torque is liable to change or in addition oil leakage is apt to occur. In order to prevent those defects, it is necessary to provide an apparatus where oil pressure is absorbed on increasing of the same.
With this kind of apparatus it has been known to have a space chamber formed in the cylinder or the rotor with a piston contained therein. Such piston is urged in one direction by a spring, so that an oil pressure absorbing chamber is formed in front of the piston. However, this type of apparatus is troublesome to assemble and is high in price.
U.S. Pat. No. 3,116,617 discloses a prior art fluid impulse torque tool.